Classifications

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  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
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  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/20—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the epoxy compounds used
  • C08G59/32—Epoxy compounds containing three or more epoxy groups
  • C08G59/3236—Heterocylic compounds
  • C08G59/3245—Heterocylic compounds containing only nitrogen as a heteroatom
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  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/20—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the epoxy compounds used
  • C08G59/32—Epoxy compounds containing three or more epoxy groups
  • C08G59/38—Epoxy compounds containing three or more epoxy groups together with di-epoxy compounds
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  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/4007—Curing agents not provided for by the groups C08G59/42 - C08G59/66
  • C08G59/4014—Nitrogen containing compounds
  • C08G59/4021—Ureas; Thioureas; Guanidines; Dicyandiamides
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  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/50—Amines
  • C08G59/5046—Amines heterocyclic
  • C08G59/5053—Amines heterocyclic containing only nitrogen as a heteroatom
  • C08G59/5073—Amines heterocyclic containing only nitrogen as a heteroatom having two nitrogen atoms in the ring
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  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/68—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the catalysts used
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  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
  • C08J5/0405—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres
  • C08J5/042—Reinforcing macromolecular compounds with loose or coherent fibrous material with inorganic fibres with carbon fibres
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  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
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  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
  • C08J5/241—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs using inorganic fibres
  • C08J5/243—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs using inorganic fibres using carbon fibres
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  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/24—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs
  • C08J5/249—Impregnating materials with prepolymers which can be polymerised in situ, e.g. manufacture of prepregs characterised by the additives used in the prepolymer mixture
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/34—Heterocyclic compounds having nitrogen in the ring
  • C08K5/3442—Heterocyclic compounds having nitrogen in the ring having two nitrogen atoms in the ring
  • C08K5/3445—Five-membered rings
• • C—CHEMISTRY; METALLURGY
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  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/55—Boron-containing compounds
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
  • C08L63/04—Epoxynovolacs
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  • C08J2363/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
  • C08J2363/02—Polyglycidyl ethers of bis-phenols
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  • C08J2463/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
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  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2463/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
  • C08J2463/06—Triglycidylisocyanurates
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  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/02—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group
  • C08L2205/025—Polymer mixtures characterised by other features containing two or more polymers of the same C08L -group containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
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  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/03—Polymer mixtures characterised by other features containing three or more polymers in a blend

Definitions

• the present invention relates to an epoxy resin composition adapted for use as matrix resin in a fiber reinforced composite material suitable for sport applications and general industry applications, and also relates to a prepreg and a fiber reinforced composite material prepared by using the epoxy resin composition as matrix resin.
• Epoxy resins have been widely used in various industries as coatings, adhesives, electric and electronic information materials, advanced composite materials, or the like because of their excellent mechanical properties. Epoxy resins have been frequently used particularly in fiber reinforced composite materials that are composed mainly of reinforcing fiber, such as carbon fiber, glass fiber, and aramid fiber, combined with matrix resin.
• a prepreg produced by impregnating a carbon fiber base with an epoxy resin is popular in the field of production of carbon fiber reinforced composite materials.
• Such a prepreg is laminated in layers or preformed, and then heated to cure the epoxy resin, thereby producing a molded article. If the curing reaction proceeds before the lamination step, the prepreg will suffer deterioration in handling property. Therefore, an epoxy resin to use in a prepreg requires high preservation stability, and dicyandiamide is widely as curing agent because it is high in latent curing property.
• carbon fiber composite materials Being lightweight and having high strength and high stiffness, carbon fiber composite materials have been used in a variety of fields ranging from sport and leisure goods to industrial applications such as automobiles and aircraft. With this feature, they have been frequently used in recent years not only in structure members, but also for texture-of-cloth decoration realized by arranging woven fabrics in surfaces. For an epoxy resin adopted as matrix resin, therefore, importance is now attached to the low colors of cured products and appearance of molded articles in addition to high heat resistance and good mechanical properties of cured products. If dicyandiamide is used as curing agent, however, there occurs the problem of white spots being formed on the surface of the resulting molded article, leading to deterioration in the appearance thereof.
• Patent document 1 discloses a technique designed to depress the formation of white spots in prepreg by adopting a masterbatch containing dicyandiamide particles with small diameters to allow the dicyandiamide and epoxy resin to be dissolved or compatibilized during the step for impregnating the base.
• Patent document 2 discloses a technique that uses polythiol and a urea compound as curing agent components and Patent document 3 discloses a technique that employs an acid anhydride as curing agent.
• An object of the present invention is to eliminate the drawbacks of these conventional techniques to provide an epoxy resin composition that serves to produce a cured epoxy resin simultaneously realizing a high heat resistance, a high elastic modulus, and a low color and to produce a molded article having a good appearance without suffering the formation of white spots on the surface thereof when used as matrix resin in a fiber reinforced composite material, and also provide a prepreg produced from the epoxy resin composition, and a fiber reinforced composite material that is obtained by curing the prepreg and that suffers no white spots on the surface thereof and has a good appearance.
• the inventors of the present invention found an epoxy resin composition having the following constitution and arrived at the present invention on the basis of the finding. More specifically, the epoxy resin composition according to the present invention has the constitution described below.
• An epoxy resin composition including an epoxy resin as component [A], an aromatic urea [B1] and/or an imidazole compound [B2] as component [B], and a borate ester compound as component [C], containing dicyandiamide in the amount of 0.5 part by mass or less relative to the total quantity of epoxy resins which accounts for 100 parts by mass, and meeting the requirement ⁇ i> or ⁇ ii> given below:
• an isocyanurate type epoxy resin [A1] is contained as component [A] in an amount of 10 to 40 parts by mass relative to the total quantity of epoxy resins which represents 100 parts by mass,
• an bisphenol type epoxy resin [A2] is contained as component [A] in an amount of 40 to 90 parts by mass relative to the total quantity of epoxy resins which represents 100 parts by mass,
• resin [A2] has an average epoxy equivalent weight of 220 to 500 g/eq
• an epoxy resin [A3] as represented by general formula (I) is contained as component [A] in an amount of 50 to 100 parts by mass relative to the total quantity of epoxy resins which represents 100 parts by mass,
• R 1 , R 2 , and R 3 each are a hydrogen atom or a methyl group, and n is an integer of 1 or more, and (e) the average epoxy equivalent weight over all epoxy resins is 165 to 265 g/eq.
• the prepreg according to the present invention is a prepreg that includes the aforementioned epoxy resin composition and reinforcing fiber.
• the fiber reinforced composite material according to the present invention is a fiber reinforced composite material that is obtainable by curing the aforementioned prepreg.
• the present invention can provide an epoxy resin composition that serves to produce a cured epoxy resin realizing a high heat resistance, good mechanical properties and a low color and to produce a molded article having a good appearance without suffering the formation of white spots on the surface thereof when used as matrix resin in a fiber reinforced composite material.
• the epoxy resin composition according to the present invention includes an epoxy resin as component [A], an aromatic urea [B1] and/or an imidazole compound [B2] as component [B], and a borate ester compound as component [C], contains dicyandiamide in the amount of 0.5 part by mass or less relative to the total quantity of epoxy resins which accounts for 100 parts by mass, and meets the requirement ⁇ i> or ⁇ ii> given below:
• an isocyanurate type epoxy resin [A1] is contained as component [A] in an amount of 10 to 40 parts by mass relative to the total quantity of epoxy resins which represents 100 parts by mass,
• an bisphenol type epoxy resin [A2] is contained as component [A] in an amount of 40 to 90 parts by mass relative to the total quantity of epoxy resins which represents 100 parts by mass,
• resin [A2] has an average epoxy equivalent weight of 220 to 500 g/eq, and
• an epoxy resin [A3] as represented by general formula (I) is contained as component [A] in an amount of 50 to 100 parts by mass relative to the total quantity of epoxy resins which represents 100 parts by mass.
• R 1 , R 2 , and R 3 are each a hydrogen atom or a methyl group, and n is an integer of 1 or more, and (e) the average epoxy equivalent weight over all epoxy resins is 165 to 265 g/eq.
• Component [A] for the present invention consists of epoxy resins.
• examples thereof include glycidyl ether type epoxy resins such as biphenyl type epoxy resins, naphthalene type epoxy resins, novolac type epoxy resins, epoxy resins having fluorene backbones, epoxy resins formed from copolymers of a phenol compound and dicyclopentadiene, diglycidyl resorcinol, tetrakis(glycidyloxyphenyl)ethane, and tris(glycidyloxyphenyl)methane; and glycidylamine type epoxy resins such as tetraglycidyl diaminodiphenylmethane, triglycidyl aminophenol, triglycidyl aminocresol, and tetraglycidyl xylene diamine.
• glycidyl ether type epoxy resins such as biphenyl type epoxy resins, naphthalene type epoxy
• component [A] an isocyanurate type epoxy resin [A1] is contained as component [A] in order to meet requirement ⁇ i>.
• component [A1] serves to produce a cured resin product having a high elastic modulus and also having an improved heat resistance, thus allowing the production of a fiber reinforced composite material having good mechanical properties and a high heat resistance.
• component [A1] It is essential for component [A1] to account for 10 to 40 parts by mass relative to the total quantity of epoxy resins, which accounts for 100 parts by mass, in the epoxy resin composition, and it is preferable that the lower limit is 15 parts by mass or more and that the upper limit is 30 parts by mass or less. As component [A1] is contained in an amount in this range, it serves to produce a cured resin product having a low color and also having an elastic modulus and a heat resistance in a good balance.
• component [A1] examples include TEPIC (registered trademark)-S, -L, -PAS B22 (all manufactured by Nissan Chemical Industries, Ltd.) and Araldite (registered trademark) PT9810 (manufactured by Huntsman Advanced Materials Gmbh).
• a bisphenol type epoxy resin [A2] is contained as component [A] in order to meet requirement ⁇ i>.
• resin [A2] serves to produce a cured resin product having a decreased color and a fiber reinforced composite material having a good appearance.
• resin [A2] It is essential for resin [A2] to account for 40 to 90 parts by mass relative to the total quantity of epoxy resins, which accounts for 100 parts by mass, in the epoxy resin composition, and it is preferable that the lower limit is 70 parts by mass or more and that the upper limit is 90 parts by mass or less. If resin [A2] is contained in an amount in this range, it serves to produce a cured resin product having a color and an elastic modulus in a good balance.
• resin [A2] examples include epoxy resins produced by glycidyl-etherification of bisphenol compounds such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, and bisphenol S type epoxy resin.
• Examples of useful commercial products of bisphenol A type epoxy resin include jER (registered trademark) 825, 828, 834, 1001, 1002, 1003, 1003F, 1004, 1004AF, 1005F, 1006FS, 1007, 1009, and 1010 (all manufactured by Mitsubishi Chemical Corporation).
• Examples of useful commercial products of bisphenol F type epoxy resin include jER (registered trademark) 806, 807, 4002P, 4004P, 4007P, 4009P, and 4010P (all manufactured by Mitsubishi Chemical Corporation), Epotohto (registered trademark) YDF2001 and YDF2004 (both manufactured by Nippon Steel Chemical Co., Ltd.), and EPICRON (registered trademark) 830, 830-S, and 835 (all manufactured by DIC Corporation).
• Examples of useful commercial products of bisphenol S type epoxy resin include EPICRON (registered trademark) EXA-1514 (manufactured by DIC Corporation).
• resin [A2] in the epoxy resin composition it is essential for resin [A2] in the epoxy resin composition to have an average epoxy equivalent weight of 220 to 500 g/eq from the viewpoint of the balance between the heat resistance and the color of the cured epoxy resin and it is preferable that the lower limit is 300 g/eq or more and that the upper limit is 400 g/eq or less. If the average epoxy equivalent weight of resin [A2] is less than 220 g/eq, the resulting cured resin will have a decreased heat resistance and an increased color, possibly leading to a fiber reinforced composite material with a poor appearance. On the other hand, if the average epoxy equivalent weight of resin [A2] is more than 500 g/eq, the color will be low, but the resulting cured resin will have a decreased heat resistance.
• the average epoxy equivalent weight of resin [A2] in the epoxy resin composition can be calculated by the method described below.
• an epoxy resin [A3] as represented by general formula (I) is contained as component [A] in order to meet requirement ⁇ ii>.
• R 1 , R 2 , and R 3 are each a hydrogen atom or a methyl group, and n is an integer of 1 or more.
• [A3] serves to produce a cured resin having a high elastic modulus and also having an improved heat resistance, thus allowing the production of a fiber reinforced composite material having good mechanical properties and a high heat resistance.
• [A3] it is essential for [A3] to account for 50 to 100 parts by mass relative to the total quantity of epoxy resins, which accounts for 100 parts by mass, in the epoxy resin composition, and it is preferable that the lower limit is 60 parts by mass or more and that the upper limit is 90 parts by mass or less.
• [A3] is contained in an amount in this range, it serves to produce a cured resin product having a low color and also having an elastic modulus and a heat resistance in a good balance.
• [A3] examples include phenol novolac type epoxy resin and cresol novolac type epoxy resin.
• phenol novolac type epoxy resin examples include jER (registered trademark) 152 and 154 (both manufactured by Mitsubishi Chemical Corporation) and EPPN-201 (manufactured by Nippon Kayaku Co., Ltd.).
• cresol novolac-type epoxy resin examples include EPICRON (registered trademark) N-660, N-665, N-670, N-673, N-680, N-690, and N-695 (all manufactured by DIC Corporation), and EOCN-102S, EOCN-103S, and EOCN-104S (all manufactured by Nippon Kayaku Co., Ltd.).
• the average epoxy equivalent weight over all epoxy resins in the epoxy resin composition is 165 to 265 g/eq in order to realize a good balance between heat resistance and color of the cured epoxy resin and it is preferable that the lower limit is 180 g/eq or more and that the upper limit is 250 g/eq or less. If the average epoxy equivalent weight over all epoxy resins is less than 165 g/eq, the resulting cured resin will have a decreased heat resistance and an increased color, possibly leading to a fiber reinforced composite material with a poor appearance. On the other hand, if the average epoxy equivalent weight over all epoxy resins is more than 265 g/eq, the color will be low, but the resulting cured resin will have a decreased heat resistance.
• the average epoxy equivalent weight over all epoxy resins in the epoxy resin composition can be calculated by the method described below.
• component [B] consists of an aromatic urea [B1] and/or an imidazole compound [B2].
• component [B] works as a curing agent to promote the self-polymerization of the epoxy resins in component [A].
• the use of component [B] serves to produce a cured epoxy resin having a low color and a good balance with heat resistance in comparison with other self-polymerization type curing agents.
• [B1] In the case where substantially only [B1] is contained as component [B], it is preferable for [B1] to account for 2.5 to 7.5 parts by mass relative to the total quantity of epoxy resins, which accounts for 100 parts by mass, in the epoxy resin composition, and it is more preferable that the lower limit is 3 parts by mass or more and that the upper limit is 7 parts by mass or less.
• the cured resin will have a decreased heat resistance if the content of [B1] is less than 2.5 parts by mass, whereas the cured resin will have an increased color, leading to a fiber reinforced composite material with a deteriorated appearance, if it is more than 7.5 parts by mass.
• [B1] and [B2] are contained as component [B]
• [B1] and [B2] account for 0.5 to 5 parts by mass and 0.5 to 5 parts by mass, respectively, relative to the total quantity of epoxy resins, which accounts for 100 parts by mass, in the epoxy resin composition and that the total content of [B1] and [B2] is 2.5 to 7.5 parts by mass.
• the lower limit is 1 part by mass or more whereas the upper limit is 4 parts by mass or less
• the lower limit is 1 part by mass or more whereas the upper limit is 4 parts by mass or less.
• the lower limit of the total content of [B1] and [B2] is 3 parts by mass or more whereas the upper limit thereof is 7 parts by mass or less.
• the cured resin will have a decreased heat resistance if the total content of [B1] and [B2] is less than 2.5 parts by mass, whereas the cured resin will have an increased color, leading to a fiber reinforced composite material with a deteriorated appearance, if it is more than 7.5 parts by mass.
• aromatic urea [B1] examples include 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, phenyl-dimethylurea, and toluene bisdimethylurea.
• Commercially available products of aromatic urea include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.) and Omicure (registered trademark) 24 (manufactured by PTI Japan).
• imidazole compound [B2] examples include 1-benzyl-2-methyl imidazole, 1-benzyl-2-ethyl imidazole, 1-cyanoethyl-2-methyl imidazole, 1-cyanoethyl-2-ethyl-4-methyl imidazole, and 1-cyanoethyl-2-phenyl imidazole. These imidazole compounds may be used singly or as a combination of two or more thereof.
• R 4 , R 5 , R 6 , and R 7 are each independently a hydrogen atom, an aliphatic hydrocarbon group with a carbon number of 1 to 20, or a phenyl group, and X is a single bond, an alkylene group, an alkylidene group, an ether group, or a sulfonyl group.
• a compound as represented by general formula (II) is an addition product obtainable through a reaction between an imidazole compound and an epoxy compound.
• Commercial products of the addition product include Cureduct (registered trademark) P-0505 (Shikoku Chemicals Corporation) and JER cure (registered trademark) P200H50 (Mitsubishi Chemical Corporation).
• the incorporation of a dicyandiamide as curing agent may result in a molded article suffering the formation of white spots on the surface thereof to deteriorate the appearance.
• the dicyandiamide it is necessary for the dicyandiamide to account for 0.5 part by mass or less, more preferably 0.2 part by mass or less, relative to the total quantity of epoxy resins, which accounts for 100 parts by mass, and it is most preferable that dicyandiamide is not contained.
• the epoxy resin composition according to the present invention it is essential for the epoxy resin composition according to the present invention to contain a borate ester compound as component [C].
• the borate ester compound of component [C] works as a stabilization agent for the aromatic urea and/or imidazole compound of component [B].
• the incorporation of a borate ester compound is desirable because it serves to produce an epoxy resin composition and a prepreg having an improved preservation stability.
• boric ester compound examples include alkyl borates such as trimethyl borate, triethyl borate, tributyl borate, tri-n-octyl borate, tri(triethylene glycol methyl ether) borate, tricyclohexyl borate, and trimenthyl borate; aromatic borate esters such as tri-o-cresyl borate, tri-m-cresyl borate, tri-p-cresyl borate, and triphenyl borate; and others such as tri(1,3-butanediol) biborate, tri(2-methyl-2,4-pentanediol) biborate, and trioctylene glycol diborate.
• alkyl borates such as trimethyl borate, triethyl borate, tributyl borate, tri-n-octyl borate, tri(triethylene glycol methyl ether) borate, tricyclohexyl borate, and trimenth
• the borate ester compound to use may also be a cyclic borate ester compound having a cyclic structure in its molecule.
• the cyclic borate ester include tris-o-phenylene bisborate, bis-o-phenylene pyroborate, bis-2,3-dimethylethylene pyroborate, and bis-2,2-dimethyltrimethylene pyroborate.
• a mixture of materials may be kneaded by using a machine such as kneader, planetary mixer, three roll mill, and twin screw extruder, or a mixture may be manually produced by using, for example, a beaker and a spatula if uniform kneading is possible.
• Preferred preparation methods include the following. Specifically, component [A] is put in a container and heated while stirring to an appropriate temperature in the range of 130° C. to 180° C. to ensure uniform dissolution of the epoxy resin. Subsequently, it is cooled while stirring preferably to a temperature of 100° C. or less, more preferably 80° C. or less, and still more preferably 60° C.
• component [B] and component [C] are fed, followed by kneading.
• a prepreg composed mainly of an epoxy resin composition and reinforcing fiber in order to ensure easy storage and high handleability.
• a prepreg can be obtained by impregnating reinforcing fiber with the epoxy resin composition according to the present invention.
• Good techniques for the impregnation include hot melting (dry method).
• Hot melting is a technique designed for direct impregnation of reinforcing fiber with an epoxy resin composition that is preliminarily heated to decrease its viscosity. Specifically, a film coated with an epoxy resin composition is first prepared on a piece of release paper or the like, and then the film is put on a sheet of paralleled reinforcing fibers or a sheet (cloth) of woven fabric reinforcing fibers from both sides or from one side thereof, and heated and pressed to ensure impregnation of the reinforcing fiber with the resin.
• the reinforcing fiber to use in a prepreg, and the various fibers listed above in the description of fiber reinforced composite materials can be adopted.
• the use of carbon fiber is preferred because it serves to provide a fiber reinforced composite material that is light in weight and high in stiffness and a molded article containing glossy black fibers and having good design characteristics.
• Fiber reinforced composite materials containing a cured product of the epoxy resin composition according to the present invention and reinforcing fiber are adopted favorably in sports applications, general industrial applications, and aerospace applications. More specifically, preferred sports applications include golf shafts, fishing rods, tennis and badminton rackets, hockey and other sticks, and skiing poles. Furthermore, preferred general industrial applications include structural and interior finishing material of vehicles (such as automobiles, motorcycles, bicycles, ships, and railroad vehicles), drive shafts, plate springs, windmill blades, pressure vessels, flywheels, rollers for paper manufacture, roofing materials, cables, and mending/reinforcing materials.
• vehicles such as automobiles, motorcycles, bicycles, ships, and railroad vehicles
• drive shafts such as automobiles, motorcycles, bicycles, ships, and railroad vehicles
• plate springs such as plate springs, windmill blades, pressure vessels, flywheels, rollers for paper manufacture, roofing materials, cables, and mending/reinforcing materials.
• Determination of physical properties was performed in an environment with a temperature of 23° C. and a relative humidity of 50% unless otherwise specified.
• [A2]-1 EPICLON (registered trademark) 830 (bisphenol F type epoxy resin, epoxy equivalent weight 172, manufactured by DIC Corporation)
• [A2]-2 jER registered trademark 828 (bisphenol A type epoxy resin, epoxy equivalent weight 189, manufactured by Mitsubishi Chemical Corporation)
• [A2]-4 jER (registered trademark) 1001 (bisphenol A type epoxy resin, epoxy equivalent weight 470, manufactured by Mitsubishi Chemical Corporation)
• [A2]-6 jER (registered trademark) 1007 bisphenol A type epoxy resin, epoxy equivalent weight 910, manufactured by Mitsubishi Chemical Corporation
• [A3]-1 jER (registered trademark) 154 phenol novolac type epoxy resin, epoxy equivalent weight 175, a compound as represented by general formula (I) wherein R 1 , R 2 , and R 3 are each a hydrogen atom, manufactured by Mitsubishi Chemical Corporation)
• Component [B] aromatic urea and/or imidazole compound
• a liquid-state epoxy resin ([A2]-1, [A2]-2, and/or [A3]-1 to be contained in the resin composition) was prepared in an amount of 10 parts by mass (accounting for 10 parts by mass relative to the total quantity of epoxy resins in component [A], which accounts for 100 parts by mass).
• an aromatic urea and/or imidazole compound of component [B], other curing agent [B′], and/or a borate ester compound of component [C] that are to be contained in the resin composition are added and kneaded in a kneader at room temperature.
• the resulting mixture was passed through a three roll mill twice to prepare a curing agent masterbatch.
• An epoxy resin composition prepared according to the ⁇ Method for preparation of epoxy resin compositions> described above was defoamed in a vacuum and cured at a temperature of 130° C. for 90 minutes in a mold set for a thickness of 2 mm using a 2 mm thick spacer of Teflon (registered trademark), thus providing a cured epoxy resin plate with a thickness of 2 mm.
• An epoxy resin composition prepared according to the ⁇ Method for preparation of epoxy resin composition> described above was spread on a piece of release paper using a film coater to produce a resin film having a metsuke of 66 g/m 2 .
• Ten plies of this woven fabric prepreg were laid up with their fibers aligned in the same direction, covered with a nylon film in a gapless manner, and subjected to heat-compression molding in an autoclave at 130° C. for 2 hours under an internal pressure of 0.3 MPa to ensure curing to prepare a woven fabric CFRP.
• the preservation stability of an epoxy resin composition is evaluated in terms of the variation in Tg that is determined as described below.
• 2 g of an epoxy resin composition prepared according to the ⁇ Method for preparation of epoxy resin composition> described above was fixed and it was stored for 7 days in a constant temperature and humidity tank placed in an environment with a temperature of 25° C. and a relative humidity of 50% RH.
• a 3 mg sample of the resin was weighed on a pan before and after the storage and measurements were taken using a differential scanning colorimeter (Q-2000, manufactured by TA Instrument) while increasing the temperature from ⁇ 50° C. to 100° C. at a constant heating rate of 10° C./minute.
• Tg glass transition temperature
• a test piece with a width of 10 mm, a length of 40 mm, and a thickness of 2 mm was cut out of a cured epoxy resin sample prepared according to the ⁇ Method for production of cured epoxy resin> described above and subjected to measurement by a dynamic viscoelasticity measuring apparatus (DMA-Q800, manufactured by TA Instruments) under the conditions of a deformation mode of cantilever bending, a span of 18 mm, a strain of 20 ⁇ m, a frequency of 1 Hz, and a constant temperature raising rate of 5° C./min for heating from 40° C. to 200° C. Tg was determined as the onset temperature of storage elastic modulus in the resulting storage elastic modulus-temperature curve.
• DMA-Q800 dynamic viscoelasticity measuring apparatus
• a 3 cm ⁇ 3 cm test piece with a thickness of 2 mm was cut out of a cured epoxy resin sample prepared according to the ⁇ Method for production of cured epoxy resin> described above.
• This test piece was subjected to measurement of the color of transmitting objects using a spectrophotometer (MSC-P, manufactured by Suga Test Instruments Co., Ltd.) according to JIS Z8722 (2009) to determine the tristimulus values.
• MSC-P spectrophotometer
• JIS Z8722 JIS Z8722
• Woven fabric CFRP was prepared according to the ⁇ Method for production of woven fabric CFRP> described above and immersed in 40° C. water for 7 days. After the immersion, the appearance of the woven fabric CFRP was observed visually focusing on the portions around intersections of fibers. A specimen was rated as good when no white spots were found and rated as poor when white spots were found.
• An epoxy resin composition was prepared according to the ⁇ Method for preparation of epoxy resin composition> described above using 20 parts by mass of TEPIC (registered trademark)-L, 25 parts by mass of jER (registered trademark) 828, and 55 parts by mass of Epotohto (registered trademark) YDF2001 as the epoxy resins of component [A], 4 parts by mass of Omicure (registered trademark) 24 as aromatic urea [B1], and 3 parts by mass of Cureduct (registered trademark) L-07N as the mixture containing a borate ester compound of component [C].
• the Tg variation was measured and found to be +4° C., which shows a high preservation stability.
• cured epoxy resin was prepared according to the ⁇ Method for production of cured epoxy resin>.
• the Tg, flexural modulus, and yellowness index of this cured epoxy resin were measured and results showed a Tg of 136° C., a flexural modulus of 3.5 GPa, and a yellowness index of 52, which suggest that the cured resin had good physical properties.
• woven fabric CFRP was prepared from the epoxy resin composition obtained and its appearance was observed. The observation showed no white spots.
• Example 1 Except for using the resin components that are shown in Tables 1, 2 and 3, the same procedure as in Example 1 was carried out to prepare epoxy resin compositions, cured epoxy resins, and woven fabric CFRPs.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 4. Evaluation results are also shown in Table 4. Good results were obtained for the preservation stability of the epoxy resin composition, the Tg and elastic modulus of the cured epoxy resins, and the appearance of the woven fabric CFRP. However, the content of [A2] was less than 40 parts by mass relative to the total quantity of epoxy resins which represented 100 parts by mass, and accordingly, condition (b) was not met although the overall constitution nearly met requirement ⁇ i>, resulting in a cured epoxy resin with a less desirable yellowness index compared to Example 1.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 4. Evaluation results are also shown in Table 4. Good results were obtained for the Tg and elastic modulus of the cured epoxy resin and the appearance of the woven fabric CFRP, but the epoxy resin composition had a lower preservation stability compared to Comparative example 1. In addition, the content of [A2] was less than 40 parts by mass relative to the total quantity of epoxy resins which represented 100 parts by mass, and accordingly, condition (b) was not met although the overall constitution nearly met requirement ⁇ i>, resulting in a cured epoxy resin with a less desirable yellowness index compared to Example 1.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 4. Evaluation results are also shown in Table 4. Good results were obtained for the preservation stability of the epoxy resin composition, the Tg and yellowness index of the cured epoxy resins, and the appearance of the woven fabric CFRP. However, the content of [A1] was less than 10 parts by mass relative to the total quantity of epoxy resins which represented 100 parts by mass, and accordingly, condition (a) was not met although the overall constitution nearly met requirement ⁇ i>, resulting in a cured epoxy resin with a smaller elastic modulus compared to Example 1.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 4. Evaluation results are also shown in Table 4. Good results were obtained for the preservation stability of the epoxy resin composition, the Tg and yellowness index of the cured epoxy resins, and the appearance of the woven fabric CFRP. However, the content of [A1] was less than 10 parts by mass relative to the total quantity of epoxy resins which represented 100 parts by mass, and accordingly, condition (a) was not met although the overall constitution nearly met requirement ⁇ i>, resulting in a cured epoxy resin with a smaller elastic modulus compared to Example 1.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 4. Evaluation results are also shown in Table 4. Good results were obtained for the preservation stability of the epoxy resin composition, the Tg of the cured epoxy resins, and the appearance of the woven fabric CFRP, but the yellowness index had an undesirable value.
• the content of [A1] was less than 10 parts by mass relative to the total quantity of epoxy resins which represented 100 parts by mass, and accordingly, condition (a) was not met although the overall constitution nearly met requirement ⁇ i>, resulting in a cured epoxy resin with a smaller elastic modulus compared to Example 1.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 4. Evaluation results are also shown in Table 4. Good results were obtained for the preservation stability of the epoxy resin composition, the Tg and elastic modulus of the cured epoxy resins, and the appearance of the woven fabric CFRP. However, the content of [A1] was more than 40 parts by mass relative to the total quantity of epoxy resins which represented 100 parts by mass, and accordingly, condition (a) was not met although the overall constitution nearly met requirement ⁇ i>, resulting in a cured epoxy resin with a less desirable yellowness index compared to Example 9.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 5. Evaluation results are also shown in Table 5. Good results were obtained for the preservation stability of the epoxy resin composition, the elastic modulus and yellowness index of the cured epoxy resins, and the appearance of the woven fabric CFRP. However, the average epoxy equivalent weight of [A2] was less than 220 g/eq, and accordingly, condition (c) was not met although the overall constitution nearly met requirement ⁇ i>, resulting in a cured epoxy resin with a lower Tg compared to Example 1.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 5. Evaluation results are also shown in Table 5. Good results were obtained for the preservation stability of the epoxy resin composition, the elastic modulus and yellowness index of the cured epoxy resins, and the appearance of the woven fabric CFRP. However, the average epoxy equivalent weight of [A2] was more than 500 g/eq, and accordingly, condition (c) was not met although the overall constitution nearly met requirement ⁇ i>, resulting in a cured epoxy resin with a lower Tg compared to Example 1.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 5. Evaluation results are also shown in Table 5. Good results were obtained for the preservation stability of the epoxy resin composition, the Tg and yellowness index of the cured epoxy resins, and the appearance of the woven fabric CFRP. However, the content of [A3] was small, and accordingly, condition (d) was not met although the overall constitution nearly met requirement ⁇ ii>, resulting in a cured epoxy resin with a smaller elastic modulus compared to Example 3.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 5. Evaluation results are also shown in Table 5. Good results were obtained for the preservation stability of the epoxy resin composition, the elastic modulus of the cured epoxy resins, and the appearance of the woven fabric CFRP. However, the average epoxy equivalent weight over all epoxy resins was less than 165 g/eq, and accordingly, condition (e) was not met although the overall constitution nearly met requirement ⁇ ii>, resulting in a cured epoxy resin with an undesirable Tg and an undesirable yellowness index compared to Example 3.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 5. Evaluation results are also shown in Table 5. Good results were obtained for the preservation stability of the epoxy resin composition, the elastic modulus and yellowness index of the cured epoxy resins, and the appearance of the woven fabric CFRP. However, the average epoxy equivalent weight over all epoxy resins was more than 265 g/eq, and accordingly, condition (e) was not met although the overall constitution nearly met requirement ⁇ ii>, resulting in a cured epoxy resin with an undesirable Tg compared to Example 3.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 5. Evaluation results are also shown in Table 5. Good results were obtained for the preservation stability of the epoxy resin composition and the Tg, elastic modulus, and yellowness index of the cured epoxy resin, but dicyandiamide was contained, resulting in white spots being found in the woven fabric CFRP.
• An epoxy resin composition, cured epoxy resin, and woven fabric CFRP were prepared by the same procedure as in Example 1 using the resin components given in Table 5. Evaluation results are also shown in Table 5. Since component [C] was not contained, the epoxy resin composition had a lower preservation stability compared to Example 3.
• Example 19 Example 20 Epoxy resin [A] [A1] TEPIC ®-S 30 30 30 composition epoxy resin isocyanurate type epoxy resin TEPIC ®-L (parts by mass) TEPIC ®-PAS B22 [A2] EPICLON ® 830 bisphenol type epoxy resin jER ® 828 25 25 25 Epotohto ® YDF2001 45 45 45 jER ® 1001 jER ® 4004P jER ® 1007 [A3] jER ® 154 epoxy resin as represented by general formula (I) [B] [B1] DCMU99 aromatic urea aromatic urea Omicure 24 2 4 8 and/or imidazole [B2] Curezol ® 2PZ compound imidazole compound Cureduct ® P-0505 [C] Cureduct ® L-07N 3 3 3 mixture containing borate ester compound Resin average epoxy equivalent weight over all epoxy resins g ⁇ eq ⁇ 1 190
• the epoxy resin composition according to the present invention serves to produce a cured epoxy resin that simultaneously realizes a high heat resistance, a high elastic modulus, and a low color and therefore, fiber reinforced composite materials containing this as matrix resin have a high heat resistance, good mechanical properties, and a low color. Furthermore, molded articles produced from such fiber reinforced composite materials do not suffer the formation of white spots on the surface thereof, and this feature, in combined with their low color feature, can ensure high designability.
• the epoxy resin composition, prepreg, and fiber reinforced composite material according to the present invention can be applied favorably to sport applications and general industrial applications.

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